The present invention is in the field of surface mats for supporting a mass and distributing its weight over a surface under the mat. More specifically, the present invention relates to performed, portable mat structures for covering a relatively large area, and designed for easy transport and rapid and repeated installation, and may be juxtaposed on a surface to provide a work apron and/or travel way.
The field long has been motivated to provide mass supporting and weight distributing temporary surfaces over suitable substrates on which heavy equipment or vehicles can be placed and operated. In the past, such temporary surfaces over unstable substrates (e.g., soft earth) were constructed of wooden planks. However, these plank structures were found to be labor intensive, time consuming to construct and expensive. Therefore, alternatives to wooden plank structures were developed. Early alternatives to plank structures included wooden mat modules that individually could be assembled into larger surface covering structures (e.g., see Davis et al, U.S. Pat. No. 4,289,420). The field recognized advantages of modular wooden mat structures and alternative wooden mat modules were developed. See Green, U.S. Pat. No. 4,376,596; Sarver; U.S. Pat. No. 4,600,337; and Pouyer, U.S. Pat. No. 5,273,373.
However wood mats had some inherent disadvantages, and recognition of these motivated tie field to develop mat modules constructed of composites and other materials as an alternative to wood. For example, Seaux, U.S. Pat. No. 5,653,551, discloses a composite mat module having partially overlapping upper and lower layers. The Seaux mats interlock with each other at their perimeter edges, where the two layers of the module do not overlap. However, this configuration means that a surface constricted of the Seaux mats will only be half as thick at its peripheral edge than it is everywhere else.
Therefore, it would be beneficial to have an alternative performed, composite mat module that can be used either individually or in an assembly and have the same mass supporting and weight distributing properties over substantially all of its surface.
The present invention is a rig mat module for bearing and distributing weight on a surface. More specifically, one or more of the present rig mat modules is to be laid on a substrate surface that otherwise cannot bear or is to be protected from the weight of an object placed on or moved across the top surface of the rig mat module. The present rig mat module may be placed singly or juxtaposed in groups to provide a weight bearing and distributing surface such as a work apron or travel/road way. A surface assembly of juxtaposed rig mat modules can be attached together at their perimeter edges to improve the stability of the surface assembly. Such surfaces can be used as crane pads, for creating a gravel-less, field work site, and for protecting relatively soft surfaces from the effects of heavy equipment use.
The present rig mat module comprises a spacer grate sandwiched between a top plate and a bottom plate. Each plate has an exposed or exterior surface, an interior surface and a perimeter edge. The plates are disposed in parallel alignment with the interior surfaces of the plates juxtaposed to define a grating space between them. The spacer grate is disposed within the grating space between the top and bottom plates and is in contact with and fixed to the interior surfaces of the top and bottom plates. An edge binder is disposed around the assemblage of the plates and spacer grate to engage the perimeter edges of the plates. The binder encloses the grating space and provides additional structural integrity to the perimeter of the assemblage.
The top and bottom plates are comprised of any suitable non-metal material as is selectable by one of ordinary skill in art in view of the teachings herein. Wood plates (e.g., plywood) or plates constructed of solid laminate plastics, fiberglass or other synthetic of composite materials may be used. Light metals, such as a metal mesh, may be embedded or molded into a plate for structural purposes or to provide gripping exterior surface to the plate. The thickness of the plates is selectable The ordinary skilled artisan depending on the anticipated loading of the rig mat module and the material construction of the plates. Also, the thickness and material of the two plates may be different each from the other. Further, the outer or exposed surfaces of the top and bottom plates may be different. For example, the exposed surface of the top plate may be a traction surface (e.g., for foot or vehicular traffic) while the exposed surface of the bottom plate is stippled to help anchor or improve its engagement with the surface on which it rests.
The spacer grate comprises a plurality of grating bars disposed relative to each other in a parallel and spaced relationship. The spaced relationship may be uniform for all grating bars or it may be varied to accommodate the expected mass load on different sections of the rig mat module. Each grating bar has a length, a width and a height. The width and the height define the cross-sectional of the grating bar, and the length defines the dimension of fire grating bars that are in parallel with each other. Typically the cross-section of the grating bar is substantially oblong. The spaced relationship of the grating bars (how far one grating bar is from an adjacent grating bar) is about 2-times to 20-times the width of the grating bar. The width of the grating bar is about 0.5 to about 1.0 inches. For large mass loads, a preferred spaced relationship is 2 with the width of the grating bar being about 0.6 inches. As with the spaced relationship of the grating bars, the width slay be uniform for all grating bars or it may be varied to accommodate the mass expected mass on different sections of the rig mat module. The height of the grating bar is about 1.0 to about 2.0 inches, and preferably about 1.5 inches. The grating bars themselves may be constricted using a pultrusion process, as is known in the art (e.g., see U.S. Pat. No. 4,522,009 to Fingerson). The grating bars also each have a plurality of rod apertures passing through the surfaces of the grating bar perpendicular to its width. The rod apertures have a thickness and are disposed in alignment with adjacent grating bars. The rod apertures are for closely passing dowel-rods therethrough. The length of the grating bars is dependent on the intended use of the rig mat module and the size of the area to be covered. It is intended in the present invention that the length of the grating bars be at least about two feet.
The spacer grate also comprises a plurality of dowel-rods disposed in a parallel spaced relationship to each other and in perpendicular relationship to the grating bars. The dowel-rods pass through the rod apertures and attach to the grating bars to fix the spaced relationship of the grating bars. A dowel-rod comprises two spacer-rods separated by a wedge-rod. A spacer-rod has an outer engagement surface and an inner flat surface. The outer engagement surface of the spacer rod has spaced engaging means for engaging the grate bar where the dowel-rod passes through the rod-aperture. The inner flat surface of the spacer rod slidably interfaces with the wedge-rod. Typically, the outer engagement surface of the spacer rod has a plurality of notches, for closely engaging the thickness of the rod-aperture as the dowel-rod passes through the grate bar. The notches are spaced apart to fix the spaced relationship of the grating bars. The wedge-rod has two similar opposite interface surfaces for slidably contacting the two spacer-rods and to hold the spacer-rods apart. Also, the wedge rod has two similar and opposite curvilinear surfaces, disposed to closely pass through the rod-apertures. The wedge-rod is adhered at the interface surface of each of the two spacer-rods.
The rig mat module of the present invention optionally comprises a coupling means for holding the perimeter edge of the rig mat module adjacent to the perimeter edge of an adjacent rig mat module. An example of a coupling means is a simple stake passing through the rig mat module proximate its perimeter in a number of location to fix adjacent rig mat modules to the underlying surface. Alternatively, the stake can have a squared xe2x80x9cUxe2x80x9d configuration and be disposed to pass through two adjacent rig mat modules at the same time. If heavy anchoring of the mat modules is required, the mat modules may further comprise anchor bores distributed over the plane of the mat module, through which heavy duty stakes may be driven to anchor the mat in place on a ground surface.
The overall dimensions of a rig mat module is selectable by the ordinary skilled artisan and defined by the dimensions of the component parts and the total number of grating bars used. Roughly, the width of a rig mat module is the length of the grating bars used, and the run or length of the rig mat module is the number of grating bars times the spaced relationship. Where the desired overall dimensions of a rig mat module is larger than the dimensions of the individual components (plates, gratings bars or cross-bars), a plurality of the individual components can be used (e.g., two grating bars in series) to accomplish the desire overall dimensions. If the dimensions of a module require that it be comprised of multiple plates on each side of the module, and the plates are asymmetric (i.e., have a grain line) the plates on opposite sides of the module may be disposed to have the asymmetry be perpendicular and off-setting
The top and bottom plate elements of the rig mat module allow a point or focused weight to be placed on the mat and distributed over multiple grating bars, which otherwise could not be placed on an open grating. Additionally, the plate covered rig mat modules of the present invention have broader utility than open grate mats on soft surfaces such as marshy or muddy soil. The thickness of the plates can be different depending on the anticipated loading of the top plate and the surface contacting the bottom plate. The plates can be a single thickness or comprised of a laminate. Additionally, either exterior surface of a plate can be layered with a cover plate which is removable. The cover plate can be utilized to provide protection to the plate under it or to increase it loading capacity. A cover plate can be replaced when worm or not needed, or can be switched out to provide a surface on the rig mat module suitable for a specific purpose (e.g., a high friction or gripping surface in a wet environment).